Study of Trigger Timing

These plots were made using Matt's SSD KS sample. Here, as in previous studies, I have selected vees with timing information on both tracks. In this case that condition was satisfied by 48% of the parent sample. The newest version of all tc (the combined straw and cerenkov timing consistency cut) has also been applied.

 

 

Here we see about 1.6% of the KS's occur in rf bucket +1. This is less that the 3.5% found in the type 1, 4 and 5 sample. One major difference is that here we know that we had at least two charged tracks pass through TR2 associated with this hadronic event. In the non-SSD sample it is possible that no charged tracks pass though TR2 associated with the hadronic event.

The 20 KS's found in rf buckets other that 0 or 1 are consistent with the random coincidence of a hadronic event in a bucket near a master gate. (See the hand-waving calculation below)

If we approximate that the instantaneous intensity is constant then we expect:


Probability of      # Triggers     # Ungated MG1     # of buckets
Random Hadronic  =  ----------  *  -------------  *  seen by one 
Coincidence          # Buckets       # Buckets       trigger.

In one spill we have...
     35000   45000             
P =  ----- * ----- * 9 = 1.4e-8
      1e9     1e9

or 14 times per spill, which means 14/35000 = 4x10-4 or 0.04% of all triggers. Then with this sample of 32000 KS's we expect about 13 random coincidences. This last step assumes that the number of KS's per hadronic event is the same for triggered and randon coincidence events, which is most likely untrue considering the MG1 is not 100% efficient for events with KS's. In any event this calculation should to yield a good lower limit.

 
 
Matt's SSD KS skim also contained a good sample of SSD Lambdas.

These plots show roughly the same fraction of Lambdas in rf bucket +1 (1.5%), but we expect about 3 events in other buckets.

 
This final set of plots show cerenkov time profiles for rf buckets 0 and 1.

Here the x axis units are in bucket periods and the plots are centered on the rf bucket in question. The solid lines are C2, the dashed are C1, and the dotted are C3.

Note the extra hump to the left of zero in the rf = 1 plot. This feature does not appear in any of the other rf buckets. It is most likely caused by triggers whose time is not set by the leading edge of the rf pulse. I plan to study the possibility that our out of time hadronic events correspond to this peak.

Questions, Comments: Jonathan Link